Our broad objectives are to define the molecular mechanisms by which steroi receptors cooperate with other factors to temporally coordinate the transcription of specific genes. These interests have lead us to the discovery of several novel glucocorticoid regulatory elements, denoted delayed secondary GREs (sGREs), that have the following features. (i) Confer hormonal inducibility upon linked reporter constructs in stably transfected mammalian cells (in vivo). This induction is specific to glucocorticoids, occurs in a time - and dose-dependent manner, is sensitive to receptor antagonist RU486, is preceded by a time lag of several hours, and is blocked by inhibitors of protein synthesis. (ii) Are negatively regulated by the hormone during the time lag. (iii) Sustain the activation of a linked promoter as effectively with transient, pulsatile exposure to hormone as with continuous exposure. (iv) Bind selectively and cooperatively via unusual sequence motifs to purified glucocorticoid receptors in vitro. (v) Remarkably, the sequence of a single receptor footprint site that binds selectively to the receptor in vitro is a delayed sGRE in vivo. Redundancy in the delayed sGRE/receptor binding site appears important for maximal induction but not for controlling the duration of the time lag. We propose to extend these findings by: constructing specific mutations affecting this element, to define at DNA sequence level the characteristics of protein-DNA interactions, and to explore possible functional relationship between the specific nucleotides that affect receptor binding and delayed sGRE activities. Studies on the first delayed secondary glucocorticoid response element to b characterized in detail at the molecular level will provide valuable insights to biology and medicine. Delayed sGREs are hormone responsive biological "clocks" generating effectors for mediation of developmental and physiological programs. Aberrations in delayed secondary response circuitr is likely to lead to biological defects including oncogenesis.